While alcoholic fermentation can be expressed by a series of enzyme-catalyzed biochemical reactions, brewing and wine-making are ancient arts practiced centuries before the science of chemistry was born. The biochemistry of wine-making was demonstrated in 1856 by Louis Pasteur when he showed that wine is produced when the simple sugars in the fruit juices are fermented by yeast, Saccharomyces cerevisiae, to yield ethanol and carbon dioxide. Vinegar was produced when the yeast cultures were contaminated by other organisms.
Beer is made in a similar manner by the fermentation of the carbohydrates present in cereal grains such as barley. These carbohydrates, largely polysaccharides, are not degraded by the glycolytic enzymes in yeast cells, which can only act on disaccharides and monosaccharides. This problem is overcome by "malting" the barley. In malting, the cereal seeds are allowed to germinate until they form the appropriate enzymes required to break down the polysaccharides of the cell walls as well as the starch and other polysaccharide food reserves within the cells of the seeds. Germination is then stopped by controlled heating. The malt now contains enzymes such as alpha amylase and maltase that are capable of breaking down the starch to maltose, glucose and other simple sugars. In the next step, the brewer prepares the "wort" by mixing the malt with water and mashing. This allows the enzymes to break down the cereal polysaccharides into the simple sugars which are soluble in the liquid medium. The remaining cell matter is then separated and the liquid wort boiled with hops to provide flavor. The yeast cells are then added. In the presence of oxygen, the yeast cells are "activated", i.e. grow and reproduce very rapidly. No ethanol is formed until all of the oxygen is utilized. Under anaerobic conditions, the yeast ferments the sugars into ethanol and carbon dioxide. This fermentation process is controlled in part by the concentration of the ethanol formed, by the pH, and by the amount of sugar present. After the fermentation has been stopped, the cells are removed and the raw beer is ready for final processing (adjustment of the amount of "head", CO.sub.2 concentration, concentration of flavorings).
Cordials and spirits are initially prepared in the same way as beer, by fermentation of a cereal mash. The alcohol produced by fermentation is the: distilled to yield a product having an alcohol content of 30-50%. The only flavoring present in the final product, for example, rum, vodka or gin, are those volatile compounds which accompany the alcohol or which are added to the concentrated alcohol.
These methods require long fermentation times and large processing and storage equipment. As can be readily seen, these requirements restrict output capacity and greatly increase the cost of both production and storage. Various processes have been tried to shorten the time required for fermentation. In almost all cases, however, such efforts result in deterioration of the aroma and flavor of the final product.
It is therefore an object of the present invention to provide a process and means for preparing a rapidly fermented alcoholic beverage which possesses all of the desirable flavor characteristics of the beverage processed by conventional methods.
It is a further object of the present invention to provide a bioreactor containing yeast allowing fermentation at an enhanced rate at a higher percentage of alcohol than is presently possible.
It is another object of the present invention to provide yeast and bacterial strains for use in the bioreactor.